Cellulosic-thermoplastic composite and method of making the same

ABSTRACT

Provided is a composition comprising fatty acid bis-amide, inorganic particulate such as pumice, cellulosic particulate, thermoplastic and maleic anhydride grafted polyolefin. The combination of an ethylene bis-amide and a minor amount of pumice produces cellulosic-thermoplastic composite that has superior extrusion properties over conventional metal stearate/ethylene bis-stearamide (EBS) compositions such as improved flex strength and resistance to water absorption.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/764,227 filed Jul. 28, 2005, which is herein incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

With the increasing scarcity of quality wood lumber, it has become mostdesirable to seek alternative materials that can substitute for wood.Composite materials prepared from plastics and natural fibers are widelyused as such wood substitutes. The use of these composite materials inarticles of commerce is increasing rapidly. These composite materialscan be used in a variety of products for structural and decorativearchitectural applications, as well as automotive uses. These compositematerials may be cut, shaped, sanded, drilled and fastened in the samemanner as natural wood.

Architectural products containing these composite materials preparedfrom plastics and natural fibers are frequently prepared by extrusion.The architectural products containing these composite materials can beused in both residential and commercial applications. Examples of suchapplications include decking, railing, fencing, posts, trim, moldings,siding, shingles, lattice, sills, and jambs. When compared to wood,consumers expect such composite materials to offer greater durabilityand weather resistance, with lower maintenance. Composite materialsprepared from plastics and natural fibers are generally resistant to rotand insect attack.

Maximizing the durability of these composite materials prepared fromplastics and natural fibers is of critical importance to consumers andproducers alike. These composite materials are generally more costlythan natural wood. Furthermore, they are also usually heavier than wood,which is a potential hardship to builders, and presents additionalstructural issues for architects and engineers. In order to overcomethese drawbacks, composite materials should offer superior benefits interms of durability and low maintenance.

Composite materials prepared from plastics and natural fibers may alsobe used for the production of articles in automotive applications. Avariety of parts have been prepared such as knobs, interior doorhandles, and decorative interior fascia; as well as concealed parts suchas sound-deadening panels, trunk liners, tire covers, bins, and carpetbackings. Such parts are frequently pressed or molded.

Other uses for composite materials prepared from plastics and naturalfibers include sheeting substitutes for fiberboard, particleboard andplywood. Composite materials can be used to make miscellaneous smallarticles such as planters, tubs, pots, and picture frames.

Useful composite materials can be prepared from various plastics,including polyethylene polypropylene and co-polyethylene-vinyl acetate.Recycled plastics are frequently used in order to lower cost.High-density polyethylene (HDPE) is particularly well-suited for use indecking, railing, fencing, and similar applications.

Natural fibers are used in the composite materials in order to reducecost and weight of the composite material, and to improve the physicalproperties, particularly stiffness and tensile strength. Natural fibersare superior to synthetic fibers like carbon and glass as the naturalfibers are of lower cost. Natural fibers are preferred over mineralfillers such as talc and mica as the natural fibers produce lightercomposites. The natural fibers are usually waste products from otherprocesses. Almost any cellulosic particulate can be used, includingwood, newspaper, cardboard, straw, agricultural and plant residues, andthe like.

A well-known problem in the formation of composite materials preparedfrom plastics and natural fibers is the incompatibility of the fiberwith the plastic. Natural fibers are hydrophilic, with many free polarhydroxyl groups on the surface. Plastics are hydrophobic. Therefore, theplastics do not readily wet the surface of the natural fiber and adherethereto. This causes a loss of strength in the resulting compositematerial.

This problem can be overcome by the addition of coupling agents to thecomposite material. Coupling agents are thought to function by thereaction of a reactive anhydride or acid moiety with hydroxyl groups onthe surface of the fiber to form an ester linkage. The hydrophobicpolymer chains extend outwards from the fiber surface, where they caninteract with the bulk of the polymer matrix. The exact nature of theinteraction will depend upon the choice of coupling agent and polymer,and the extent of crystallinity of the polymer. The coupling agentgenerally serves as a transitional bridge that improves the adhesion ofthe plastic to the natural fiber surface. Improved adhesion can resultin improved physical properties for the composite material prepared fromplastics and natural fibers, particularly the tensile and flexuralstrength, resistance to water absorption and creep, and reduction in thelinear coefficient of thermal expansion (LCTE).

If the composite material prepared from plastics and natural fibersmaterial is to be processed by extrusion, a lubricant is normally addedto aid in passage of the composite material from the die. An improperlylubricated system will cause the composite material to extrude atdiffering rates. This can result in various unacceptable physicaldefects in the composite material, ranging from a scaly sharkskinappearance to saw-toothed edge tears.

A commonly used lubricant system is a blend of zinc stearate with anN,N′-ethylene bis-stearamide (EBS) wax. Other lubricants include calciumstearate, magnesium stearate, non-metallic stearates; paraffin wax,polyester wax, polypropylene wax, fatty acid derived bis-amides,ethylene bis-oleamide, esters such as stearyl stearate, distearylphthalate, pentaerythritol adipate stearate, ethylene glycol distearate,pentaerythritol tetrastearate, glycerol tristearate, polyethylene glycol400 monostearate, glycerol monooleate, glycerol distearate, and blendedcomplex modified fatty acid esters.

Unfortunately, it has been found that the commonly used zincstearate-EBS lubricant system interferes with the coupling agent. It hasbeen suggested that the zinc stearate is responsible for theinterference with the maleic anhydride grafted olefin coupling agents.The stearate ring opens and esterifies the anhydride group, while thezinc complexes the resulting carboxylate. The coupling agent thenprovides significantly less improvement to the physical properties ofthe composite material prepared from plastics and natural fibers thanexpected.

Some commercial composite materials prepared from plastics and naturalfibers use a zinc stearate/ethylene bis-stearamide lubricant systemwithout any coupling agent. These formulations extrude quite readily,and provide product of excellent appearance. The physical properties ofthese composites are deficient when compared to those of natural wood.

2. Description of Related Art

U.S. Pat. No. 6,632,863 claims a two-step process whereby wood-plasticcomposite (WPC) pellets are made which may contain from 0 to 35% of anadditive selected from a group of inorganic fillers and lubricants. Thelubricants are subsequently selected from the group of zinc stearate andethylene bis-stearamide. The inorganic fillers are subsequently selectedfrom the group of talc and mica. The WPC pellet is subsequentlyre-extruded with additional plastic and additives.

U.S. Pat. Nos. 6,498,205 and 6,344,504 claim a WPC prepared from apowder blend of wood fiber/flour, plastic, and a lubricant selected fromzinc stearate and a wax. The specifications give ethylene bis-stearamideas an example of a wax.

U.S. Pat. Nos. 6,682,789 and 6,265,037 and U.S. patent application Ser.No. 2001/0051243 teach a polymer/fiber composite composition, a processfor WPC manufacture, and disclose an extruded profile thereby prepared,based on polyolefins prepared by modern metallocene catalysis with adistribution ratio (M_(w)/M_(n)) of 3 to 6, a melt index of less than 2gm/10 min, where moisture content is less than 5000 parts per million(ppm) of the formulation, and the fiber dimensions are from 100 to 2000micrometers (μm), with an aspect ratio of 1:2 to about 1:5. Maleicanhydride grafted olefin coupling agents are used, and the compositionmay contain lubricants and inorganic fillers.

U.S. patent application Ser. No. 2003/0229160 teaches that ethylenebis-amides made from carboxylic acids of 6 to 10 carbons are superiorlubricants to EBS/zinc stearate blends presently used in wood. Thisapplication further teaches a composite comprising about 30 to about 70weight percent polymer, about 70 to about 30 weight percent agriculturalwaste fiber, and about 1 to 7 weight percent of a lubricant consistingof an amide, an alkylene bisamide, or a combination thereof.

U.S. Pat. No. 4,791,020 teaches the use of up to 40% inorganic filler ina WPC, where the filler is selected from the group consisting of mica,talc, calcium carbonate, silica, glass fiber, asbestos and wollastonite.

U.S. Pat. No. 5,326,513 teaches a process for producing plastic fiberboards using a material selected from balls of expanded glass, expandedclay, pumice granules and mica, admixed with a foaming and hardenableorganic and inorganic binder, where the organic binder is an epoxy resinor a polyurethane phenol resin.

U.S. Pat. No. 5,516,472 describes a process (“Strandex Process”) widelylicensed and used in the WPC industry. The patent teaches that thepreferred formulation to be used with the above process includes 3.0parts zinc stearate and 2.0 parts external (paraffin-type) wax perhundred parts wood flour.

BRIEF SUMMARY OF THE INVENTION

The prior art implies that the removal of metal stearates from compositeformulation would be desirable. The prior art does not teach that thiscan be accomplished while retaining the familiar, inexpensive, andwidely used ethylene bis-stearamide in the formulation.

This invention relates to a composition that aids in the processing andmanufacture of cellulosic-thermoplastic composite. This composition isan unexpected and synergistic combination of fatty acid bis-amide (a) ofthe structure:

where R¹ and R² are independently saturated or unsaturated linearhydrocarbyl groups containing from about 11 to about 35 carbon atoms,inorganic particulate (b), cellulosic particulate (c), thermoplastic (d)and coupling agent (e) for coupling cellulosic particulate (c) to thethermoplastic (d).

This invention also relates to a method of extruding the combination offatty acid bis-amide (a), inorganic particulate (b), cellulosicparticulate (c), thermoplastic (d) and coupling agent (e) through anextruder to provide cellulosic-thermoplastic composite.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a graph of the output vs extruder speed for example 1 andcomparative example A; and

FIG. 2 is a graph of the output vs extruder speed for example 2 andcomparative example G.

DETAILED DESCRIPTION OF THE INVENTION

It is most desirable to be able to use coupling agent in formulation ofcellulosic-thenmoplastic composites. Coupling agent can providesignificant improvements in the physical properties ofcellulosic-thenmoplastic composites. Although, increased difficulty isencountered in extruding cellulosic-thermoplastic composites containingcoupling agent, which requires the use of additional lubricant.Additional lubricant can significantly reduce the expected improvementsin physical properties.

We have unexpectedly found that the use of coupling agent (e) incombination with fatty acid bis-amide (a) and minor amount of finelypowdered pumice overcomes these processing issues, permitting acellulosic-thermoplastic composite of fully satisfactory appearance tobe extruded at a rate comparable to that obtained with a comparativeformulation containing zinc stearate/ethylene bis-stearamide and nocoupling agent.

Fatty acid bis-amide (a) acts as a lubricant that does not impairfunctioning of coupling agent (e) that is present. Fatty acid bis-amide(a) structure, as described above, where R¹ and R² can be independentlysaturated or unsaturated linear hydrocarbyl groups containing from 11 to35 carbon atoms. Preferably R¹ and R² are independently saturated orunsaturated linear hydrocarbyl groups containing from 15 to 22 carbonatoms. Some examples of fatty acid bis-amide (a) can be N,N′-ethylenebis-stearamide (N,N′-ethylene bis-octadecanamide), N,N′-ethylenebis-oleamide (N,N′-ethylene bis-cis-9-octadecenamide), N,N′-ethylenebis-dodecanamide, N,N′-ethylene bis-tetradecanamide, N,N′-ethylenebis-hexadecanamide, N,N′-ethylene bis-heptadecanamide, N,N′-ethylenebis-tallowamide, N,N′-ethylene bis-eicosanamide, N,N′-ethylenebis-docosanamide, N,N′-ethylene bis-tetracosanamide, N,N′-ethylenebis-4-dodecenamide, N,N′-ethylene bis-9-dodecenamide, N,N′-ethylenebis-4-tetradecenamide, N,N′-ethylene bis-5-tetradecenamide,N,N′-ethylene bis-cis-6-octadeceneamide, N,N′-ethylenebis-trans-6-octadeceneamide, N,N′-ethylene bis-cis -9-octadeceneamide,N,N′-ethylene bis-trans-9-octadeceneamide, N,N′-ethylene bis-trans-11-octadeceneamide, N,N′-ethylene bis-cis-9-eicosenamide, N,N′-ethylenebis-cis-11-eicosenamide, N,N′-ethylene bis-trans-11-eicosenamide,N,N′-ethylene bis-cis-11-docosenamide, N,N′-ethylenebis-cis-13-docosenamide, N,N′-ethylene bis-trans-13-docosenamide,N,N′-ethylene bis-cis-15-tetracosenamide and combinations thereof Itwill also be recognized by one skilled in the art that the various mixedcross reaction products of N,N′-ethylenediamine with two or more of theparent fatty acid used to prepare the preceeding bis amide may also beused e.g. N-oleyl-N′-stearyl- ethylene-bis-amide. A person skilled inthe art will understand that such a cross reaction product can beprepared by reacting N,N′-ethylenediamine with a naturally occurringmixture of fatty acids, such as the acids derived from tallow. A personskilled in the art will understand that a single fatty acid bis-amide(a) can be used or two or more of such fatty acid bis amide (a) can beused.

Inorganic particulate (b) can be any inorganic particulate that canimpart lubrication to the composition. The lubrication is such that itcan facilitate the extrusion of cellulosic-thermoplastic composite at anequivalent rate compared to conventional zinc stearate/EBS lubricantcompositions that are not used with coupling agent (e). Examples ofsuitable inorganic particulate (b) can be pumice, volcanic ash, alumina,diatomaceous earth, glass, silica, titanium oxide, iron oxide, zincoxide, magnesium oxide, ceramic materials, calcium silicate hydrates,microspheres, perlite, shirua basalt, zeolites, clay, kaolin,metakaolin, mica, calcium carbonate, wollastonite, talc, titaniumdioxide, barium sulfate, calcium sulfate, acrylics, vermiculite, flyash, microspheres, gypsum, calcium aluminate, xonotlite, magnesia andcombinations thereof. Preferred inorganic particulate (b) can be pumice.Most preferred inorganic particulate (b) can be finely powdered pumice,for example, those produced by VitroCo (Vitrolite®), Elkem (Sidistar®),Hess and combinations thereof. A person skilled in the art willunderstand that a single inorganic particulate (b) can be used or two ormore of such inorganic particulate (b) can be used. Inorganicparticulate (b) can generally be of a particle size of 50 μm or less,preferably 35 μm or less and more preferably 20 μm or less.

Cellulosic particulate (c) can be any known, conventional, orcommercially used cellulosic particulate that can be used incellulosic-thermoplastic composites. Examples of suitable cellulosicparticulate (c) can be wood fiber, wood particles, wood chips, groundwood, wood flour, wood flakes, wood veneers, wood laminates, saw dust,paper, newspaper, cardboard, wood pulp fiber, chemical pulp, recycledpaper fiber, recycled boxes, recycled box fiber, recycled newspaper,recycled newspaper fiber, recycled computer printout, recycled computerprintout fiber, milling tailings, hardwood fiber, softwood fiber,newsprint, ground newsprint, magazines, ground magazines, books, groundbooks, ground cardboard, wheat chaff, bamboo fiber, pond sludge, corkand combinations thereof. Preferably, cellulosic particulate (c) isselected from the group consisting of wood fiber, wood flour andcombinations thereof. It will be understood by a person skilled in theart that wood pulp can be any known wood pulp material, for example,thermo mechanical wood pulp, chemical thenno mechanical wood pulp andcombinations thereof. A person skilled in the art will understand that asingle cellulosic particulate (c) can be used or two or more of suchcellulosic particulate (c) can be used. Cellulosic particulate (c) cangenerally be from about 3 mm to about 100 μm in length and from about 1mm to about 100 μin width. Preferably cellulosic particulate (c) can befrom about 1 mm to about 400 μm in length and from about 500 μm to about100 μm in width. More preferably, cellulosic particulate (c) can be fromabout 800 μm to about 200 μm in length and from about 400 μm to about100 μm width. Cellulosic particulate (c) can generally have an aspectratio of from about 20:1 to about 1:1. Preferably, cellulosicparticulate (c) can have an aspect ratio of from about 10:1 to about1:1. More preferably, cellulosic particulate (c) can have an aspectratio of from about 5:1 to about 2:1.

Thermoplastic (d) can be any polymer, and preferably is polyolefin andmore preferably can be polyethylene, polypropylene, copolymers ofethylene and propylene, copolymers of polyethylene and vinyl acetate andcombinations thereof. More preferably, thermoplastic (d) is selectedfrom the group consisting of high-density polyethylene, low-densitypolyethylene, linear low-density polyethylene, polypropylene, copolymersof ethylene and propylene, co-polyethylene-vinyl acetate andcombinations thereof.

As noted above, it is most desirable to be able to use coupling agent(e) in formulation of natural fiber-plastic composites. Coupling agentcan provide significant improvements in physical properties ofcellulosic-thermoplastic composites. Improvements are most noticeable inthe flex strength and resistance to water absorption ofcellulosic-thermoplastic composites.

Improved flex strength is important, as natural wood has much higherflex strength than the polymer matrix, and cellulosic-thermoplasticcomposites must have strength properties that are similar to naturalwood if they are to be used in architectural applications. Improvedwater resistance correlates with resistance to rot, and so is also ofutmost importance for products intended for exterior applications.Reductions in creep and LCTE improve the dimensional stability ofcellulosic-thermoplastic composite, and therefore its suitability forarchitectural uses.

These improvements in physical properties are readily observed in moldedtest specimens. Increased difficulty is encountered in extrudingcellulosic-thermoplastic composite containing coupling agent. Thisrequires the use of additional lubricant, which as noted above, cansignificantly reduce expected improvements in physical properties.

We have unexpectedly found that the use of coupling agent (e) incombination with fatty acid bis-amide (a) and a minor amount of finelypowdered pumice overcomes these processing issues, permittingcellulosic-thermoplastic composite of fully satisfactory appearance tobe extruded at a rate comparable to that obtained with a comparativeformulation containing zinc stearate/ethylene bis-stearamide and nocoupling agent. The flex strength and resistance to water absorption ofcellulosic-thermoplastic composite of this invention are significantlybetter than the comparative formulation.

Coupling agent (e) can be maleic anhydride grafted polyolefin, acrylicacid grafted polyolefin, vinyl acetate grafted polyolefin andcombinations thereof. Preferably coupling agent (e) can be maleicanhydride grafted high-density polyethylene, maleic anhydride graftedlow-density polyethylene, maleic anhydride grafted polypropylene,acrylic acid grafted high-density polyethylene, acrylic acid graftedlow-density polyethylene, acrylic acid grafted polypropylene,co-polyethylene-vinyl acetate and combinations thereof.

Coupling agent (e) most preferably is selected from the group consistingof maleic anhydride grafted (“maleated”) high-density polyethylene(Polybond® 3009, Polbond® 3029, Polybond® 3039), maleic anhydridegrafted linear low-density polyethylene (Polybond® 3109), maleicanhydride grafted polypropylene (Polybond® 3000, Polybond® 3200), acrlicacid grafted high-density polyethylene (Polybond® 1009), acrylic acidgrafted polypropylene (Polybond® 1001, Polybond® 1002) and combinationsthereof; all available from Chemtura Corporation.

The composition can also contain at least one additional component.Examples of a suitable additional component can be antioxidant, UVstabilizer, foaming agent, dye, pigment, cross-linking agent, inhibitor,and accelerator. In addition further inorganic particulate may be usedas filler. Any further inorganic filler may be used provided it does notinterfere with extrusion.

Antioxidants are added to prevent degradation of polymer duringprocessing. An example is Chemtura Corporation's Naugard B25 (a mixtureof tris (2,4-di-tert-butyl phenyl) phosphite and tetrakis methylene(3,5-Di-tert-butyl-4-hydroxyhydrocinnamate) methane). Foaming agent isadded to decrease density of the cellulosic-thermoplastic composite byfoaming. Examples of foaming agents are Chemtura Corporation's Celogen®TSH (toluene sulfonyl hydrazide), Celogen AZ (azodicarbonamide), CelogenOT (p-p′-oxybis(benzenesulfonylhydrazide)), Celogen RA (p-toluenesulfonyl semicarbazide), Opex® 80 (dinitrosopentamethyleetetramine), andExpandex® 5-PT (5-phenyltetrazole).

Colorants are pigments or dyes. Dyes are commonly an organic compoundsoluble in plastic forming a neutral molecular solution. They producebright intense colors and are transparent. Pigments are generallyinsoluble in plastic. The color results from the dispersion of fineparticles (in the range of about 0.01 to about 1 μm) throughoutthermoplastic (d). They produce opacity or at least some translucence incellulosic-thennoplastic composite. Pigments can be organic or inorganiccompounds and are viable in a variety of forms including dry powders,color concentrates, liquids and precolor resin pellets. Most commoninorganic pigments include oxides, sulfides, chromates, and othercomplexes based on a heavy metal such as cadmium, zinc, titanium, lead,molybdenum, iron, combinations thereof, and others. Ultramarines aretypically sulfide-silicate complexes containing sodium and aluminum.Often pigments comprise mixtures of two, three or more oxides of iron,barium, titanium, antimony, nickel, chromium, lead, and others in knownratios. Titanium dioxide is a widely used and known bright whitethermally stable inorganic pigment. Organic pigments are also knownincluding azo or diazo pigments, pyrazolone pigments, and othersincluding permanent red 2B, nickel azo yellow, litho red, and pigmentscarlet.

Cross-linking agent can optionally be added to strengthen the bondbetween cellulosic particulate (c), as described above, into a finalhomogenous product. Cross-linking agent bonds across the pendenthydroxyl groups on the cellulose molecular chain. Cross-linking agentmust have the characteristics of forming a strong bond at relatively lowtemperatures. Examples of cross-linking agent that can be used includepolyurethanes such as isocyanate, phenolic resin, unsaturated polyesterand epoxy resin and combinations thereof. Phenolic resin may be anysingle stage or two-stage resin preferably with low hexane content.

Inhibitor is added to retard the speed of the cross-linking reaction.Examples of known inhibitors include organic acids such as citric acid.

Accelerator is added to increase the speed of the cross-linkingreaction. Examples of accelerators include amine catalysts such asDabco® BDO (Air Products), and DEH40® (Dow Chemical).

The amounts of the various components of the composition can be adjustedby those skilled in the art depending on the specific materials beingused and the intended use of the material. In one embodiment, thepresent invention is directed to a composition comprising fatty acidbis-amide (a) present in an amount of from about 1 to about 8 weightpercent, inorganic particulate (b) present in an amount of from about0.25 to about 1.5 weight percent, cellulosic particulate (c) present inan amount of from about 10 to about 90 weight percent, thermoplastic (d)present in an amount of from about 90 to about 10 weight percent,coupling agent (e) present in an amount of from about 0.2 to about 10weight percent.

In another embodiment, the present invention is directed to acomposition comprising fatty acid bis-amide (a) present in an amount offrom about 1 to about 8 weight percent, inorganic particulate (b)present in an amount of from about 0.25 to about 1.5 weight percent,cellulosic particulate (c) present in an amount of from about 20 toabout 80 weight percent, thermoplastic (d) present in an amount of fromabout 80 to about 20 weight percent, coupling agent (e) selected fromthe group consisting of maleic anhydride grafted polyolefin couplingagent present in an amount of from about 0.5 to about 5 weight percent,and acrylic acid grafted polyolefin coupling agent present in an amountof from about 1 to about 7 weight percent, and combinations thereof.

In yet another embodiment, the present invention is directed to acomposition comprising fatty acid bis-amide (a) present in an amount offrom about 2 to about 6 weight percent, inorganic particulate (b)present in an amount of from about 0.25 to about 1.0 weight percent,cellulosic particulate (c) present in an amount of from about 40 toabout 70 weight percent, thermoplastic (d) present in an amount of fromabout 50 to about 30 weight percent, and coupling agent (e) which ismaleic anhydride grafted high-density polyethylene coupling agentpresent in an amount of from about 1.0 to about 3 weight percent.

In yet still another embodiment the present invention is directed to acomposition comprising fatty acid bis-amide (a) selected from the groupconsisting of N,N′-ethylene bis-stearamide, N,N′-ethylene bis-oleamideand combinations thereof present in an amount of from about 1 to about 8weight percent; inorganic particulate (b) which is finely powderedpumice present in an amount of from about 0.25 to about 1.5 weightpercent; cellulosic particulate (c) selected from the group consistingof wood flour, wood fiber and combinations thereof present in an amountof from about 10 to about 90 weight percent; thermoplastic (d) selectedfrom the group consisting of high-density polyethylene, low-densitypolyethylene, linear low-density polyethylene, polypropylene, copolymersof ethylene and propylene, copolymers of polyethylene and vinyl acetateand combinations thereof present in an amount of from about 90 to about10 weight percent; and coupling agent (e) which is maleic anhydridegrafted high-density polyethylene present in an amount of from about 0.2to about 10 weight percent.

In a preferred embodiment the present invention is directed to acomposition comprising fatty acid bis-amide (a) selected from the groupconsisting of N,N′-ethylene bis-stearamide, N,N′-ethylene bis-oleamideand combinations thereof present in an amount of from about 1 to about 8weight percent; inorganic particulate (b) which is finely powderedpumice present in an amount of from about 0.25 to about 1.5 weightpercent; cellulosic particulate (c) selected from the group consistingof wood flour, wood fiber and combinations thereof present in an amountof from about 20 to about 80 weight percent; thermoplastic (d) selectedfrom the group consisting of high-density polyethylene, low-densitypolyethylene, linear low-density polyethylene, polypropylene, copolymersof ethylene and propylene, copolymers of polyethylene and vinyl acetateand combinations thereof present in an amount of from about 80 to about20 weight percent; and coupling agent (e) which is maleic anhydridegrafted high-density polyethylene present in an amount of from about 0.5to about 5 weight percent.

In more preferred embodiment the present invention is directed to acomposition comprising fatty acid bis-amide (a) selected from the groupconsisting of N,N′-ethylene bis-stearamide, N,N′-ethylene bis-oleamideand combinations thereof present in an amount of from about 2 to about 6weight percent; inorganic particulate (b) which is finely powderedpumice present in an amount of from about 0.25 to about 1.0 weightpercent; cellulosic particulate (c) selected from the group consistingof wood flour, wood fiber and combinations thereof present in an amountof from about 40 to about 70 weight percent; thermoplastic (d) selectedfrom the group consisting of high-density polyethylene, low-densitypolyethylene, linear low-density polyethylene, polypropylene, copolymersof ethylene and propylene, copolymers of polyethylene and vinyl acetateand combinations thereof present in an amount of from about 50 to about30 weight percent; and coupling agent (e) which is maleic anhydridegrafted high-density polyethylene present in an amount of from about 1.0to about 3 weight percent.

The most preferred embodiment of the present invention is directed to acomposition comprising fatty acid bis-amide (a) which is ethylenebis-stearamide is present in an amount of about 2 to about 6 weightpercent; inorganic particulate (b) which is finely powdered pumice ispresent in an amount of about 0.5 to about 1.0 weight percent;cellulosic particulate (c) which is pine wood flour 40 mesh is presentin an amount of about 45 to about 65 weight percent, thermoplastic (d)which is high density polyethylene is present in an amount of about 40to about 31 weight percent; and coupling agent (e) which is maleicanhydride grafted high-density polyethylene is present in an amount ofabout 1.5 to about 2.5 weight percent, where said grafted high-densitypolyethylene contains succinyl anhydride moieties in an amount of about0.5 to about 2.0 weight percent.

The composition can be used to make an article. The article can be solidor hollow cellulosic-thermoplastic composite profile, board, rod,strand, pellet, siding, sheet, or combination thereof.

The composition can be compounded and blended by any standard means aswill be apparent to one skilled in the art. In one method, thecombination of fatty acid bis-amide (a), inorganic particulate (b),cellulosic particulate (c), thermoplastic (d) and coupling agent (e) canbe extruded through an extruder to provide cellulosic-thermoplasticcomposite. The composition can be extruded at a temperature sufficientto melt the thermoplastic (d), and then extruded through a die to formcellulosic-thermoplastic composite. The composition can be processedthrough an extruder at a temperature of from about 145° C. to about 200°C.

There are numerous extrusion processes practiced by those skilled in theart. Practitioners frequently choose to pre-blend fiber and plastic,particularly wood and plastic, and extrude this mixture into pre-blendmaterial, or purchase such pre-blend material from a supplier, and thenfeed this pre-blend material into the final product process. Thecomposition herein may be used in such a two-pass process whereincellulosic particulate (c) and thermoplastic (d) are combined inpre-blend material in comparable ratios. Some examples of comparableratios of cellulosic particulate (c) to thermoplastic (d) can be fromabout 80:20 to about 10:90, preferably, from about 70:30 to about 20:80and more preferably from about 60:40 to about 30:70. Compositionscontaining comparable ratios of cellulosic particulate (c) tothermoplastic (d) can be from about 60:40 to about 40:60 are mostpreferred. Pre-blend material of cellulosic particulate (c) andthermoplastic (d) can be in the form of mix, pellet, flake, chip,pastille, granules and combinations thereof. Similarly, fatty acidbis-amide (a) and inorganic particulate (b) can be combined in pre-blendmaterial in comparable ratios. Some examples of comparable ratios offatty acid bis-amide (a) to inorganic particulate (b) can be from about40:60 to about 97:3, preferably, from about 67:33 to about 96:4 and morepreferably from about 67:33 to about 92:8. Compositions containingcomparable ratios of fatty acid bis-amide (a) to inorganic particulate(b) of from about 67:33 to about 92:8 are most preferred. Pre-blendmaterial of fatty acid bis-amide (a) and inorganic particulate (b) canalso be in the form of mix, pellet, flake, chip, pastille, granules andcombinations thereof. It will be understood by a person skilled in theart that pre-blend material of cellulosic particulate (c) andthermoplastic (d) and/or pre-blend material of fatty acid bis-amide (a)and inorganic particulate (b) may contain any of the other componentsprovided herein. Such additional components may be added to the chosenpre-blend(s) based upon desired processing and/or storage needs of theuser.

In a specific embodiment herein fatty acid bis-amide (a), inorganicparticulate (b), cellulosic particulate (c), thermoplastic(d) andcoupling agent (e) are combined in the substantial absence of metalsoaps, such as metal carboxylate; and more specifically, they arecombined in the substantial absence of metal stearates such as zincstearate. Cellulosic-thermoplastic composite is useful as material foruse in structural and decorative products for residential and commercialarchitecture, such as decking, railings, fences, posts, trim, siding,shingles and the like. Cellulosic-thermoplastic composite can also beused for the production of articles in automotive applications such asknobs, handles, interior fascia, sound-deadening panels and carpetbackings. Articles prepared from cellulosic-thermoplastic compositecontaining the above described composition have improved performance,such as improved flex strength and improved resistance to waterabsorption when compared to commonly used natural fiber-plasticcomposites.

As will be seen in the examples, when EBS and pumice are used inconjunction with coupling agent (e) in cellulosic-thermoplasticcomposite, a 38% improvement in flex strength over a zinc stearate/EBSsystem is observed. Furthermore a 28% reduction in 24-hour waterabsorption is also observed.

EXAMPLES

Test formulations were prepared using American Wood Fibers 4020 pinewood flour (40 mesh). The wood was dried in a circulating oven at 121°C. for 24 hours. Resulting moisture content was less than 1%.Thermoplastic (d) resin was BP Solvay B54-60 frac-melt high-densitypolyethylene (0.5 g/10 min Melt Flow), used as received. ChemturaPolybond® 3029 maleic anhydride grafted HDPE coupling agent (1.3%succinyl anhydride, Melt Flow Rating=4 g/10 min, 190 C, 2.16 kg),Naugard® B-25 antioxidant, Lubrazinc® W (zinc stearate) lubricant, andKemamide® EBS (ethylene bis-stearamide) were all used as received.VitroCo Vitrolite®XP powdered pumice was used as received. LuzenacAmerica Silverline® 403 talc was used as received.

All samples were extruded using a Brabender® Intelli-TorquePlasti-Corder® with a co-rotating #403 conical twin-screw configuration,and a Brabender 7150 drive unit. Zone temperatures were set at: Zone 1(150° C.), Zone 2 (160° C.), Zone 3 (160° C.), Zone 4 (die) (150° C.).The die produces a continuous flat test specimen 1.0″ wide and 0.080″thick. Data was acquired using Brabender Measuring Extruder BasicProgram with Multiple Evaluation, Version 3.2.1. Compounded formulationswere fed into the extruder from a K-Tron K2VT20 volumetric feeder.Specimens were extruded at 60 rpm, and in some cases at 80, and 100 rpmas well.

Maleic anhydride content of the coupling agent was determined bydissolving it in boiling toluene and titrating to a Bromothymol Blue endpoint using a standard 0.3N methanolic KOH solution. The KOH titrant wasstandardized using benzoic acid. The number of milliequivalents of KOHtitrant needed to neutralize one hundred grams of coupling agent wasdetermined. The percent maleic anhydride in the coupling agent was thencalculated assuming one mole of KOH neutralized one mole of maleicanhydride. This assumption was confirmed by titration of straight maleicanhydride under the same conditions that the coupling agents were testedunder. The number of millimoles of functionality per 100 grams ofcoupling agent was calculated by dividing the percent maleic anhydrideby the molecular weight of the chemical, which was 98 grams per mole(g/mol) and multiplying by 1000.

The Melt Flow Index of the coupling agent was determined using a TiniusOlsen Extrusion Plastometer Model MP600 following the proceduresoutlined in ASTM D1238.

A modified ASTM D790 test procedure was used to generate the flexuralstrength and flexural modulus data. In this modified procedure across-head speed of 0.5 inches per minute (in/min) was used instead ofthe standard 0.05 inches per minute.

Water absorption was determined by immersing a 1.0-inch by 2.0-inchstrip of extrudate in tap water for 24 hours at room temperature andmeasuring the weight gain.

Test formulations are presented in Table 1. Test data from specimensextruded at 60 rotations per minute (rpm) are presented in Table 2.FIGS. 1 and 2 were plotted using MINITAB® V.14.13 (Minitab Inc.).

TABLE 1 TPW- SXT- Example PB3029 % ZnSt % EBS % Pumice % Talc % WP2200 %113 % 3100 % Wood % HDPE % B-25 AO % 1 2.0 4.0 0.75 60 33.15 0.1 2 2.00.75 4.0 60 33.15 0.1 A 2.0 4.0 60 33.15 0.1 B 2.0 2.0 2.0 60 33.90 0.1C 2.0 2.0 2.0 0.75 60 35.15 0.1 D 2.0 2.0 60 35.90 0.1 E 2.0 0.75 4.0 6033.15 0.1 F 2.0 0.75 4.0 60 33.15 0.1 G 2.0 4.0 60 33.90 0.1 H 4.0 0.7560 35.15 0.1 I 2.0 0.75 4.0 60 33.15 0.1 J 2.0 4.0 3.0 60 30.90 0.1PB3029 is maleated high-density polyethylene produced by Chemtura.WP2200 is ethylene bis-lauramide produced by Lonza. TPW is a proprietarymetallic stearate free material produced by Ferro. SXT is a non-metallicstearate produced by Struktol. B-25 is Naugard ® B-25 antioxidant. Allpercentages are reported in terms of weight percent.

TABLE 2 Flex Strength Output MPa(mega % Water Abs Example ft/minPascals) 24 h 1 1.88 33.1 6.9 2 2.73 31.2 3.9 A 1.71 30.6 5.7 B 2.1323.3 9.0 C 2.01 20.8 9.7 D 1.86 23.9 9.6 E 2.30 27.7 6.9 F 2.28 25.4 6.5G 2.16 31.6 5.8 H 2.11 28.4 10.6 I 1.99 34.9 6.9 J 1.67 28.2 6.7

The performance advantage that is obtained by employing a maleicanhydride grafted coupling agent in the absence of zinc stearate isstriking. The average flex strength for the eight formulations withPolybond® 3029 coupling agent but without zinc stearate (1, 2, A, E, F,G, I, J) is 30.3 MPa, while the three formulations containing zincstearate (B, C, D) average only 22.7 MPa. Similarly, the waterabsorption in 24 hours for the eight formulations with coupling agentbut without zinc stearate is 6.2%, as compared to 9.4% for the threeformulations containing zinc stearate. Comparing B, C, and D shows thatthe advantage of using coupling agent has been lost to interference fromthe zinc stearate.

The additional advantage of using coupling agent in combination withfatty ethylene bis-amide lubricant as compared to an ester ornon-metallic stearate lubricant is seen in the flex strength comparisonbetween the average of the coupling agent/ethylene bis-amideformulations 1, 2, A, G, I, J (31.6 MPa) and the average of the couplingagent with the other lubricants E and F (26.6 MPa).

The advantage of adding pumice to the formulation is shown in FIGS. 1and 2. In each case a 15 to 20% increase in product output rate isobtained with the additional lubricant.

The advantage of pumice over another inorganic particulate (b), talc, isshown in Comparative Examples I and J. Comparative Example I, at 0.75%talc had good physical properties, but it did not extrude properly, andexhibited severe edge tear. Comparative Example J at 3.0% talc had theslowest extrusion rate of all samples, and moderately reduced flexstrength of 28.2 MPa.

While the above description contains many specifics, these specificsshould not be construed as limitations of the invention, but merely asexemplifications of preferred embodiments thereof. Those skilled in theart will envision many other embodiments within the scope and spirit ofthe invention as defined by the claims appended hereto.

1. A composition comprising: (a) from about 1 to about 8 weight percentof a fatty acid bis-amide of the structure:

where R¹ and R² are independently saturated or unsaturated linearhydrocarbyl groups containing from 11 to 35 carbon atoms, (b) from about0.25 to 0.75 weight percent of an inorganic particulate, (c) from about10 to about 90 weight percent of a cellulosic particulate from about 1mm to about 100 μm in length, (d) from about 90 to about 10 weightpercent of a thermoplastic; and, (e) from about 0.2 to about 10 weightpercent of a coupling agent for coupling cellulosic particulate (c) tothermoplastic (d), wherein the composition contains no lubricantscomprising zinc stearate and said inorganic particulate is finelypowdered pumice having a particle size of 50 μm or less.
 2. Thecomposition of claim 1 wherein R¹ and R² are independently saturated orunsaturated linear hydrocarbyl groups containing from 15 to 22 carbonatoms.
 3. The composition of claim 1 wherein fatty acid bis-amide (a) isselected from the group consisting of N,N′-ethylene bis-stearamide,N,N′-ethylene bis-oleamide, N,N′-ethylene bis-dodecanamide,N,N′-ethylene bis-tetradecanamide, N,N′-ethylene bis-hexadecanamide,N,N′-ethylene bis-tetradecanamide, N,N′-ethylene bis-tallowamide,N,N′-ethylene bis-eicosanamide, N,N′-ethylene bis-docosanamide,N,N′-ethylene bis-tetracosanamide, N,N′-ethylene bis-4-dodecenamide,N,N′-ethylene bis-9-dodecenamide, N,N′-ethylene bis-4-tetradecenamide,N,N′-ethylene bis-5-tetradecenamide, N,N′-ethylenebis-cis-6-octadeceneamide, N,N′-ethylene bis-trans-6-octadeceneamide,N,N′-ethylene bis-cis-9-octadeceneamide, N,N′-ethylenebis-trans-9-octadeceneamide, N,N′-ethylene bis-trans-11-octadeceneamide,N,N′-ethylene bis-cis-9-eicosenamide, N,N′-ethylenebis-cis-11-eicosenamide, N,N′-ethylene bis-trans-11-eicosenamide,N,N′-ethylene bis-cis-11-docosenamide, N,N′-ethylenebis-cis-13-docosenamide, N,N′-ethylene bis-trans-13-docosenamide,N,N′-ethylene bis-cis-15-tetracosenamide and combinations thereof. 4.The composition of claim 1 wherein fatty acid bis-amide (a) is a crossreaction product of N,N′-ethylenediamine with two or more fatty acids.5. The composition of claim 4 wherein fatty acid bis-amide (a) isN-oleyl-N′-stearyl-ethylene-bis-amide.
 6. The composition of claim 1wherein cellulosic particulate (c) is selected from the group consistingof wood fiber, wood particles, wood chips, ground wood, wood flour, woodflakes, wood veneers, wood laminates, saw dust, paper, newspaper,cardboard, wood pulp fiber, chemical pulp, recycled paper fiber,recycled boxes, recycled box fiber, recycled newspaper, recyclednewspaper fiber, recycled computer printout, recycled computer printoutfiber, milling tailings, hardwood fiber, softwood fiber, newsprint,ground newsprint, magazines, ground magazines, books, ground books,ground cardboard, wheat chaff, bamboo fiber, pond sludge, cork andcombinations thereof.
 7. The composition of claim 1 whereinthermoplastic (d) is selected from the group consisting of high-densitypolyethylene, low-density polyethylene, linear low-density polyethylene,polypropylene, copolymers of ethylene and propylene,co-polyethylene-vinyl acetate and combinations thereof.
 8. Thecomposition of claim 1 wherein coupling agent (e) is selected from thegroup consisting of maleic anhydride grafted polyolefin, acrylic acidgrafted polyolefin, vinyl acetate grafted polyolefin and combinationsthereof.
 9. The composition of claim 1 wherein coupling agent (e) isselected from the group consisting of maleic anhydride graftedhigh-density polyethylene, maleic anhydride grafted low-densitypolyethylene, maleic anhydride grafted polypropylene, acrylic acidgrafted high-density polyethylene, acrylic acid grafted low-densitypolyethylene, acrylic acid grafted polypropylene, co-polyethylene-vinylacetate and combinations thereof.
 10. The composition of claim 1containing at least one additional component which is selected from thegroup consisting of antioxidant, foaming agent, dye, pigment,cross-linking agent, inhibitor and accelerator.
 11. The composition ofclaim 1 wherein fatty acid bis-amide (a) is present in an amount of fromabout 1 to about 8 weight percent, inorganic particulate (b) is presentin an amount of 0.75 weight percent, cellulosic particulate (c) ispresent in an amount of from about 20 to about 80 weight percent,thermoplastic (d) is present in an amount of from about 80 to about 20weight percent, coupling agent (e) is selected from the group consistingof maleic anhydride grafted polyolefin present in an amount of fromabout 0.5 to about 5 weight percent and acrylic acid grafted polyolefinpresent in an amount of from about 1 to about 7 weight percent andcombinations thereof.
 12. The composition of claim 1 wherein fatty acidbis-amide (a) is present in an amount of from about 2 to about 6 weightpercent, inorganic particulate (b) is present in an amount of 0.75weight percent, cellulosic particulate (c) is present in an amount offrom about 40 to about 70 weight percent, thermoplastic (d) is presentin an amount of from about 50 to about 30 weight percent, and couplingagent (e) which is maleic anhydride grafted high-density polyethylenepresent in an amount of from about 1.0 to about 3 weight percent. 13.The composition of claim 1 wherein fatty acid bis-amide (a) is selectedfrom the group consisting of N,N′-ethylene bis-stearamide, N,N′-ethylenebis-oleamide and combinations thereof and is present in an amount offrom about 1 to about 8 weight percent; inorganic particulate (b) ispresent in an amount of 0.75 weight percent; cellulosic particulate (c)is selected from the group consisting of wood flour, wood fiber andcombinations thereof present in an amount of from about 10 to about 90weight percent, thermoplastic (d) is selected from the group consistingof high-density polyethylene, low-density polyethylene, linearlow-density polyethylene, polypropylene, copolymers of ethylene andpropylene, copolymers of polyethylene and vinyl acetate, andcombinations thereof present in an amount of from about 90 to about 10weight percent; and coupling agent (e) which is maleic anhydride graftedhigh-density polyethylene present in an amount of from about 0.2 toabout 10 weight percent.
 14. The composition of claim 1 wherein fattyacid bis-amide (a) is selected from the group consisting ofN,N′-ethylene bis-stearamide, N,N′-ethylene bis-oleamide andcombinations thereof present in an amount of from about 1 to about 8weight percent; inorganic particulate (b) is present in an amount of0.75 weight percent; cellulosic particulate (c) is selected from thegroup consisting of wood flour, wood fiber and combinations thereofpresent in an amount of from about 20 to about 80 weight percent;thermoplastic (d) is selected from the group consisting of high-densitypolyethylene, low-density polyethylene, linear low-density polyethylene,polypropylene, copolymers of ethylene and propylene, copolymers ofpolyethylene and vinyl acetate, and combinations thereof present in anamount of from about 80 to about 20 weight percent; and coupling agent(e) is maleic anhydride grafted high-density polyethylene present in anamount of from about 0.5 to about 5 weight percent.
 15. The compositionof claim 1 wherein fatty acid bis-amide (a) is selected from the groupconsisting of N,N′-ethylene bis-stearamide, N,N′-ethylene bis-oleamideand combinations thereof and is present in an amount of from about 2 toabout 6 weight percent; inorganic particulate (b) is present in anamount of 0.75 weight percent; cellulosic particulate (c) is selectedfrom the group consisting of wood flour, wood fiber and combinationsthereof present in an amount of from about 40 to about 70 weightpercent; thermoplastic (d) is selected from the group consisting ofhigh-density polyethylene, low-density polyethylene, linear low-densitypolyethylene, polypropylene, copolymers of ethylene and propylene,copolymers of polyethylene and vinyl acetate, and combinations thereofpresent in an amount of from about 50 to about 30 weight percent; andcoupling agent (e) which is maleic anhydride grafted high-densitypolyethylene present in an amount of from about 1.0 to about 3 weightpercent.
 16. The composition of claim 1 wherein fatty acid bis-amide (a)is ethylene bis-stearamide present in an amount of about 2 to about 6weight percent; inorganic particulate (b) is present in an amount of0.75 weight percent; cellulosic particulate (c) which is pine wood flour40 mesh is present in an amount of about 45 to about 65 weight percent,thermoplastic (d) which is high density polyethylene is present in anamount of about 40 to about 31 weight percent; and coupling agent (e)which is maleic anhydride grafted high-density polyethylene, containingabout 0.5 to about 2.0 weight percent succinyl anhydride moieties, ispresent in an amount of about 1.5 to about 2.5 weight percent.
 17. Anarticle fabricated from the composition of claim 1 wherein said articleis selected from the group consisting of solid or hollowcellulosic-thermoplastic composite profile, board, rod, strand, pellet,siding, sheet and combinations thereof.